In a connection-oriented network with a Generalised Multi-Protocol Label Switching (GMPLS) control plane it is possible to establish a connection, called a Label Switched Path (LSP), between network nodes. It is desirable that a network is resilient to the failure of a span (link) between nodes, or to a node. GMPLS includes signalling extensions which support recovery. Recovery provides a way of detecting a failure on a working path, signalling the occurrence of the failure, and then transferring traffic from the working path LSP to a recovery path.
It is possible to recover an end-to-end Label Switched Path (LSP). This is called end-to-end recovery and is defined in IETF document [RFC4872] “RSVP-TE Extensions in Support of End-to-End Generalized Multi-Protocol Label Switching (GMPLS) Recovery”. It is also possible to recover a part of an end-to-end LSP. This is called segment recovery and is defined in IETF document [RFC4873] “GMPLS Segment Recovery”.
Known recovery methods include using pre-planned (PP) recovery paths, or using pre planned with a back up in case of failure of the pre-planned route. The back up can be a computation on the fly (OTF) of a new recovery path. Alternatively the OTF can be the primary recovery path without any back up PP path.